Apparatus and method for controlling the fuel supply of a gas-fueled engine

ABSTRACT

An integrated premixture chamber is disclosed, for mixing gaseous fuel and air for delivery to a combustion chamber of an internal combustion engine. The integrated premixture chamber includes a mass air flow sensor, a throttle valve and position sensor, a fuel shut-off valve, a gas flow sensor and a fuel metering valve having discharge outlets downstream of the mass air flow sensor to provide more accurate metering. The integrated premixture chamber is controlled by an electronic unit separate from the engine&#39;s control unit.

FIELD OF THE INVENTION

The present invention relates in general to internal combustion engines,and more particularly to an apparatus and method for controlling thesupply and ignition of compressible gaseous fuels in internal combustionengines.

BACKGROUND OF THE INVENTION

The increase in atmospheric pollution generated by exhaust emissionsfrom conventional gasoline and diesel powered internal combustionengines have caused both federal and state governments to enact laws andestablish regulations which impose even greater restrictions on theperformance of motor vehicles in the areas of exhaust gas emission andfuel economy. As a result, over the past several years the automotiveindustry has increased its interest in using alternative fuels to meetthe governmental emission requirements and fuel economy standards(CAFE), and to reduce dependence on foreign oil. Alternative fuels beinginvestigated for potential use in automotive vehicles include compressednatural gas (CNG), liquid petroleum gas (LPG) and the like.

Alternative fuels typically have less energy per unit volume thangasoline or diesel fuel. However, they are generally advantageous sincegaseous fuels are cleaner burning fuels. Gaseous fuels generate lessnoxious emissions than gasoline and diesel fuels and are able to bettermeet the increasingly rigorous governmental regulations.

Great strides have been made in developing control systems andcomponents for gaseous fuel engines to meet the current governmentrequirements. But, despite recent developments and the advantages of gasas a cleaner burning fuel, the exhaust emissions of a gaseous fuelengine still contain an undesirable amount of non-methane hydrocarbons,dust particle components and unburned hydrocarbons (methane). Moreover,the noxious emissions from gaseous fuel engines must be further reducedfrom current levels to meet future exhaust emission regulations.

In order to minimize the noxious emissions of gaseous fuel engines tomeet future requirements, it is necessary to maintain an optimizedair/fuel mixture for such engines at or near a selected point, such asthe stoichiometric or a lean burn point. However, it has been difficultto accurately control the air/fuel mixture in a gaseous fuel enginebecause heretofore, the fuel injection systems have not been able toprovide sufficiently accurate metering and control.

A typical gaseous fuel injection systems includes a pressurized fuelstorage tank, a pressure regulator for reducing the fuel from arelatively high storage pressure to a lower working pressure (about oneatmosphere), a fuel metering valve for controlling the gas supply to theengine, an air/gas mixer at the engine air intake and an enginemanagement system for overall control and proper engine operation.Problems occur due to the fact that the injection of gaseous fuel intothe intake manifold of the engine, where it is mixed with air, issensitive to variations in manifold pressure, gas temperature and gaspressure caused by engine operating and environmental conditions. Suchvariations require extensive control techniques in order to maintain thedesired quantity of injected fuel over the wide range of engineoperating conditions. In addition, the fuel flow rate, which is muchhigher than in a conventional gasoline engine, requires a metering valveto control the flow rate over a large range, reducing its accuracy.Finally, the mixing of gaseous fuel and air produces problems simply dueto the inherent difficulty of gas to gas mixing.

For accurate fuel metering, a combination of a digital and analog valvehas been proposed. However, this type of valve is inherently complicatedand difficult to control, and expensive to produce. Moreover, movementwithin the digital valve (or the duty cycle injector connected thereto)affects gas flow sensing accuracy. Installing a fuel valve at eachcylinder injector aids in accurate fuel metering since the fuel flowrate is decreased due to the fact that several valves (one at eachcylinder injector) are used instead of the one valve at the throttle.However, because the injector and intake valve are close together, thereisn't sufficient time to mix the air and fuel thoroughly.

Accordingly, what is needed is an improved gaseous fuel injection systemthat will reduce noxious exhaust emissions and increase fuel consumptionby accurately controlling the supply and ignition of the air/fuelmixture.

It is, therefore, a principal object of the present invention to providea gaseous fuel injection system in which the air/fuel mixture can beaccurately controlled to provide for increased fuel economy and reducedexhaust emission through a leaner burn operation.

It is another object of the present invention to provide a gaseous fuelinjection system in which the air/fuel mixture can be accuratelycontrolled to provide for maximum torque during various operatingconditions of the engine.

It is a further object of the present invention to provide a gaseousfuel engine having increased fuel economy through a lighter weight,compact design fuel injection system.

It is still another object of the present invention to accomplish theabove-stated objects by utilizing an apparatus which is simple in designand use, and economical to manufacture.

The foregoing objects and advantages of the invention are illustrativeof those which can be achieved by the present invention and are notintended to be exhaustive or limiting of the possible advantages whichcan be realized. Thus, these and other objects and advantages of theinvention will be apparent from the description herein or can be learnedfrom practicing the invention, both as embodied herein or as modified inview of any variations which may be apparent to those skilled in theart. Accordingly, the present invention resides in the novel methods,arrangements, combinations and improvements herein shown and described.

SUMMARY OF THE INVENTION

In accordance with these and other objects of the invention, a briefsummary of the present invention is presented. Some simplifications andomissions may be made in the following summary, which is intended tohighlight and introduce some aspects of the present invention, but notto limit its scope. Detailed descriptions of a preferred exemplaryembodiment adequate to allow those of ordinary skill in the art to makeand use the inventive concepts will follow in later sections.

According to a broad aspect of the invention, an apparatus and methodfor operating an internal combustion engine having an alternative fuelsupply source is disclosed. An integrated premixture chamber is providedfor mixing gaseous fuel and air for delivery to a combustion chamber ofan internal combustion engine through an air intake passageway such asan intake manifold. The integrated premixture chamber includes an airflow sensor disposed in the air intake passageway for detecting theamount of air moving through the air intake passageway; a gas flowsensor for detecting the amount of gaseous fuel supplied to thecombustion chamber; a gas valve responsive to the gas flow sensor andhaving at least one outlet disposed in the air intake passagewaydownstream of the air flow sensor, for selectively controlling theamount of gaseous fuel supplied to the combustion chamber; a throttlevalve, having a pivotally secured plate disposed in the air intakepassageway downstream of the outlet of the gas valve, for regulating thequantity of fluid flow through the air intake passageway; a throttleposition sensor responsive to varying positions in the throttle plate,for actuating the gas valve to provide gaseous fuel in response to thethrottle plate position; and a processor for controlling the operationof the gas valve, the processor being responsive to at least the airflow sensor, the gas flow sensor and the throttle position sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram illustrating a preferred embodiment ofthe present invention mounted in an internal combustion engine.

FIG. 2 is a perspective diagram of a cross-sectional view of a preferredembodiment of the present invention.

FIGS. 3a-3f are perspective diagrams of cross-sectional views of severalembodiments gas flow sensor according to the present invention.

FIGS. 4a-4b are perspective diagrams of cross-sectional views ofpreferred embodiments of the present invention.

FIG. 5 is a block form diagram of the control systems, according to thepresent invention.

FIG. 6 is a block form diagram of the operative arrangement of thecomponents of the present invention.

FIG. 7 is a flow diagram of the operation of a gas flow sensor,according to the present invention.

FIGS. 8a-8b are perspective diagrams of another embodiment of thepresent invention mounted in an internal combustion engine.

FIG. 9 is a graphical form diagram representative of the resultsachieved in accordance with the present invention.

FIGS. 10a-10b are perspective diagrams of yet another embodiment of thepresent invention mounted in an internal combustion engine.

FIG. 11 is a perspective diagram of another embodiment of a gas meteringvalve according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention contemplates an improved gaseous fuel enginehaving an integrated premixture chamber in which the air/fuel mixture isaccurately controlled to provide for a more leaner burn of the fuel toreduce noxious exhaust emissions and decrease fuel consumption.

It is to be understood that the present invention may be used with equalfacility and advantage with various gaseous fuels such as CNG, LPG,propane or the like, and that the following description of a CNG fuelengine, related to but not forming part of the invention, is providedfor illustrative purposes only.

Referring now to the drawings, wherein like numerals refer to likeelements, there is disclosed in FIG. 1 broad aspects of a preferredembodiment of the invention. In FIG. 1, a CNG engine fuel control systemhaving an integrated premixture chamber identified generally byreference numeral 1 in accordance with the present invention is shown.The CNG fuel engine is only shown partially because the internal detailsof the engine, except for its integrated premixture chamber 1 andrelated controls, does not form part of the invention. However, aportion of the CNG fuel engine is depicted for ease in understanding howthe present invention may be practiced in conjunction with any knowntypes of internal combustion engines. It also should be noted that theintegrated premixture chamber 1 is not limited to use in reciprocatingengines of the type depicted but may be also employed with rotary typeengines. Additionally, the invention is described in conjunction withonly a single cylinder of a multi-cylinder engine, as it is believedthat those skilled in the art can readily understand how the inventionis practiced in conjunction with multiple cylinder engines and enginesof varying configurations.

The integrated premixture chamber 1 is installed in the intake passageof the CNG fuel engine. Air is introduced in series through an aircleaner 24, passed the turbines 26 of a turbocharger 27, through anintercooler 25, and into the integrated premixture chamber 1. At theintegrated premixture chamber 1, CNG fuel is introduced through at leastone and preferably a plurality of aperture outlets or orifices 7 forcontrolled mixing with the air. The gas/air mixture is driven passed thepivotal plate of a throttle valve 16 that provides selective flow to theengine's combustion chamber in predetermined quantities in response tothe movement of the vehicle accelerator pedal, transmittedelectronically or through suitable linkage to the throttle valve 16. Inthe case of an electronically linked accelerator, the operation ofthrottle valve 16 is controlled by a sub-control unit 32. Regardless ofthe type of accelerator linkage, information with respect to theposition of the throttle valve 16 is input to the sub-control unit 32via a throttle position sensing unit 20 of the type common in theindustry. Although depicted in block form in FIG. 1, the sub-controlunit 32 is preferably mounted on the integrated premixture chamber 1, inclose proximity to the various sensors and components described herein.

As described in detail below, the sub-control unit 32 also oversees theoperation of a gas shut off valve 13 and a gas metering valve 9. Thesub-control unit 32, in turn, communicates with a main-control unit 33,regarding the control and operation of the integrated premixturechamber 1. The main-control unit 33 further provides engine feedback andcontrol through the ignition of spark plug 28 mounted in the cylinderhead, and through the continuous monitoring of a lambda (O₂) exhaustsensor 29 mounted in the exhaust passage of the engine for detecting theamount of oxygen in the exhaust, a coolant temperature sensor 30 mountedon the side of the cylinder block, and a crank angle sensor (not shownfor clarity), all using conventional sensor devices and methodsunderstood by those skilled in the art.

The integrated premixture chamber 1 is in the fluid communication withthe engine's combustion chamber such that the gas/air mixture passes anintake valve when opened into the combustion chamber for ignition.Exhaust gases are discharged out of the exhaust side of the combustionchamber through an exhaust valve into an exhaust passage thatcommunicates with the turbocharger 27, and finally through a catalyticconverter 31. The catalytic converter 31 includes a catalyst bed foroxidizing carbon monoxide (CO) and hydrocarbons (HC) while deoxidizingnitrous oxide (NOx), as is commonly practiced. The exhaust gases thustreated are then discharged into the atmosphere through an exhaust pipeand suitable exhaust and muffler system (not shown).

The components of the integrated premixture chamber 1 shown in FIG. 1are best understood by referring to the chamber's 1 operativearrangement illustrated in detail in FIG. 2. As illustrated in FIG. 2, apreferred embodiment of the integrated premixture chamber 1 includes anaxial lumen 19 having a generally circular opening therethrough anddefined by intake manifold walls 18. The integrated premixture chamber 1also includes a mass air flow sensor 6 located at the upstream (withrespect to the flow of air, designated generally by the arrow A) endthereof. The mass air flow sensor 6 has connecting passageways 2 and 5,in which a hot wire 3 and a cold wire 4 are respectively located. Thehot wire 3 and cold wire 4 may be physically the same, made from asuitable metal or alloy of metals, coated by glass. As is conventionallypracticed in the art, the cold wire 4 is used to measure the intake airtemperature. Conversely, the hot wire 3 is used in a thermal process tomeasure the air flow. The electrical power dissipated by the hot wire 3resistance (i.e., the current), to maintain a constant temperature asthe air flows passed, is proportional to the air mass flow rate.Accordingly, variations in the current in hot wire 3 are used to measurethe mass air flow.

In the case when an optional turbo charger 27 is used with the CNGengine, variations of the intake air temperature are greatly increased,and the temperature of intake manifold wall is increased as well.Advantageously, in a preferred embodiment of the invention, thepassageways 2 and 5 of the mass air flow sensor 6 are separated from theintake manifold wall 18, so that the effect of air temperaturevariations on the accuracy of the mass air flow sensor 6 is minimized.The measured variations of the mass air flow sensor 6 are monitored bythe sub-control unit 32.

Gaseous fuel is supplied to the integrated premixture chamber 1 fromfuel supply tanks having a pressure regulator (not shown) via apreferably metal conduit into a shut-off valve 13 secured to theintegrated premixture chamber 1, The shut-off valve 13 is a low pressurevalve having a ball 14 mounted in a fuel passageway 15 that normallyseats in a valve seat (not shown for clarity) to block the fuel flowthrough the passageway 15. The shut-off valve 13, which can be switchedbetween open or closed positions, is controlled by the sub-control unit32 to selectively permit the flow of fuel, such as when the vehicle'signition is engaged.

The shut-off valve 13 communicates with a gas flow sensor 12, alsosecured to the integrated premixture chamber 1, for monitoring the flowof gaseous fuel. Turning briefly to FIG. 3, there is disclosed in detailseveral embodiments of the gas flow sensor 12. As illustrated in FIG.3a, the gas flow sensor 12 may be constructed in the well known mannerof providing a hot wire 52 and a cold wire 53. As practiced in the art,the current variation due to the power dissipated in keeping the hotwire 52 temperature constant is measured as a function of the mass flowof the gaseous fuel. This information is communicated to the sub-controlunit 32.

FIG. 3b illustrates another embodiment of the gas flow sensor 12, inwhich the hot wire 52 and the cold wire 53 are located in a longitudinallumen 56 defined by a housing indicated generally by the numeral 55. Gasflowing through the lumen 56 is restricted by the opening of a nozzle54, so that the upper limit of the range of detection of the gas flowsensor 12 is not exceeded. By restricting the gas flow such that theupper limit of the sensor's 12 detection range is not reached, a greateraccuracy of the flow measurement is achieved. As can be understood, thecross-sectional area of the lumen 56 will vary in accordance with thecross-section area of the main gas flow conduit 11, and the measurementrange of the sensor 12 itself.

FIG. 3c discloses yet another embodiment of the gas flow sensor 12. Thisembodimemt is similar to the embodiment illustrated in FIG. 3b, andincludes a nozzle 54 having a gradually expanding inner surface toreduce the turbulence of the gas in the lumen 56 and thereby provide formore accurate and consistent measurements.

FIGS. 3d-3f disclose additional embodiments of the gas flow sensor 12that provide further reductions in the turbulence of gas in the lumen56. FIGS. 3d-3f illustrate embodiments of gas flow sensor 12 similar tothe embodiments illustrated in FIGS. 3b and 3c, having, however, anozzle 54 on the downstream side of housing 55 rather than the upstreamside. By providing the nozzle 54 downstream of hot wire 52 and cold wire53, gas flowing through the lumen 56 undergoes compression rather thanexpansion about the wires 52, 53. As can be appreciated by those skilledin the art, expansion of the gas causes turbulence whereas compressionprovides for more stability and therefore a more accurate measurement ofthe gas flow. Accordingly, the embodiments illustrated in FIGS. 3d-3fprovide for an improved accuracy in gas flow sensor 12, by having thenozzle 54 restriction downstream of the hot and cold wires 52, 53.

FIG. 3e discloses an embodiment of the gas flow sensor 12 having anozzle in the downstream position, wherein the inner surfaces of thenozzle 54 are gradually decreased to further reduce gas turbulence.

FIG. 3f provides an embodiment of gas flow sensor 12 secured to conduit11 by bolts 57 having therebelow O-rings (not shown for clarity), toprovide for increased reliability and ease of replacement whennecessary.

Due to the similarity of the embodiments illustrated in FIGS. 3c-3f withthat illustrated in FIG. 3b, further description of these embodiments isnot believed to be necessary to understand the construction andoperation of the gas flow sensor 12. Additionally, it should beunderstood that the gas flow sensor 12 of the present invention is notlimited to the above-disclosed embodiments, and that any suitable fluidflow sensor or transducer may be employed which provides an outputsignal indicative of the fuel flow in the fuel delivery conduit 11.

Turning back to FIG. 2, the gas flow conduit of gas flow sensor 12 is influid communication with a gas metering valve 9. The gas metering valve9 continuously varies the flow of gaseous fuel under the control of thesub-control unit 32, in accordance with engine speed, exhaust oxygenlevels, the flow rate feedback provided by the gas flow sensor 12, andthrottle position data provided by the throttle sensing unit 20. Themetering valve 9 varies the fluid flow of the gaseous fuel to apassageway 10 using suitable means common to those skilled in the art.Passageway 10 communicates with the lumen 19 of the integratedpremixture chamber 1 through at least one orifice 7, and preferably aplurality of orifices 7.

As illustrated in the preferred embodiment of the invention, theintegrated premixture chamber 1 includes three orifices 7 locateddownstream of the mass air flow sensor 6. Here, CNG fuel, for example,is homogeneously mixed with the intake air. Because of the downstreamlocation of orifices 7, the CNG fuel does not measurably affect theaccuracy of the mass air flow sensor 6.

The integrated premixture chamber 1 further includes the throttle valve16 positioned downstream of the orifices 7, and which is controlledremotely by linkage or electronically in response to accelerator pedalmovement. The supply of intermixed gas and air to the engine'scombustion chamber is regulated by the throttle valve 16, as is wellknown in the industry. The throttle position sensor 20, mounted on theintegrated premixture chamber 1, as shown in FIGS. 1 and 2, providesthrottle plate position information to the sub-control unit 32 to assistin the overall operation of the engine.

In FIG. 4a, the integrated premixture chamber 1 is shown alongside across-sectional view of the chamber 1 taken along the line AA. In thepreferred embodiment disclosed, the orifices 7 contain a generallyelliptical opening due to their somewhat tangential configuration withrespect to the chamber's lumen 19. The orifices 7 are connected topassageway 10 by a generally circular passageway 8 that circumscribesthe lumen 19 and provides fluid communication therebetween. As depictedby the darkened arrows shown in the cross-sectional view in FIG. 4a,this arrangement causes the gaseous fuel discharged from the orifices 7to swirl about the lumen 19 during mixture with the air. The swirlingflow during the gas-air intermix provides a positive turbulence thatresults in a more homogenous gas/air mixture and, as is well known, amore efficient combustion.

FIG. 4b discloses another embodiment of the present invention, in whichthe lumen 19 contains a diametrically restricted area 17 adjacent to theorifices 7. Due to the larger area downstream of the restriction 17, aventuri effect is created during the swirling mixture, as the gas andair are allowed to expand downstream of the restriction 17. Theexpansion of the gases causes further positive turbulence that aids inthe homogenizing of the gas and air.

Turning now to FIG. 5, the elements of a preferred embodiment of thesub-control-unit 32 are diagramatically shown in block form. Thesub-control unit 32 receives input signals from the mass air flow sensor6, the gas flow sensor 12 and the throttle sensing unit 20. Optionally,electronic feedback of other sensors, for example, an accelerator pedalopening sensor, may also be provided to the sub-control unit 32.

The sub-control unit 32 includes an analog-to-digital converter 61 forreceiving the above-described analog sensor signals and converting theminto digital representations, as is well known in the art. These digitalsignals are communicated via a common bus to a central processing unit("CPU") 62 for executing predetermined data processing, and to a memory63 preferably consisting of read-only memory (ROM) for storing necessarydata constants and programs to be executed by the CPU 62, and a randomaccess memory (RAM) for storing data to be processed by the CPU 62 andto process results obtained during execution of the programs.

The results of the CPU's 62 processing are communicated via the commonbus to output circuitry 65 for controlling, for example, the meteringvalve 9, the shutoff valve 13 and the throttle valve 16 (in the case ofelectronic control). The processing results are also communicated viathe common bus to a communication port 64 for interfacing with the maincontrol unit 33.

The main control unit 33, like the sub-control unit 32, includes ananalog-to-digital converter 66, a CPU 67, memory 70, a communicationport 68 and an output circuit 69. The functions of these components aresimilar to the functions performed by the identically designatedcomponents of the sub-control unit 32, and therefore do not requireadditional discussion. Noticeably, the main-controller 33 receives inputsignals from, inter alia, the lambda (O₂) sensor 29, the coolanttemperature sensor 30, and the crank angle sensor. These signals areprocessed by the main-controller 33 and may be communicated to thesub-control unit 32 during overall engine operation. As can beappreciated, various other ambient or engine conditions may be suppliedto the sub-control unit 32, the main-control unit 33, or any combinationof both for overall general operation of the engine, without departingfrom the scope of the invention.

In addition, the sub-control unit 32 and main-control unit 33contemplated by the present invention may be implementedprogrammatically or by direct electrical connection through customizedintegrated circuits, or a combination of both, using any of the methodsknown in the industry for providing the functions described abovewithout departing from the teachings of the invention. Those skilled inthe art will appreciate that from the disclosure of the inventionprovided herein, commercial semiconductor integrated circuit technologywould suggest numerous alternatives for actual implementation of thefunctions of the sub-control unit 32 and main-control unit 33 that wouldstill be within the scope of the invention.

Turning now to FIG. 6, the operative control of a preferred embodimentof the invention is shown in block diagram form. Beginning at the top,data from an engine speed sensor 72, such as a tachometer, and datarepresentative of the accelerator pedal opening are combined tocalculate the engine torque demand and create a corresponding throttleopening map 70. From the throttle opening map 70, a throttle openingtarget is communicated to the throttle valve 16 to meet the torquedemand of the engine. The opening of the throttle valve 16 is based onthe opening map 70 and feedback of the throttle plate position from thethrottle sensing unit 20. As a result of the throttle valve opening, airis introduced through the intake manifold 74 to the integratedpremixture chamber 1 to be combined with the gaseous fuel for deliveryto the CNG engine.

For the delivery of fuel, air flow data is provided by mass air flowsensor 6 along with engine speed data (from the engine speed sensor 72)to create a lambda map 77, as is currently practiced in the art. Lambdais a ratio of fuel-air measurements used to determine the fuel needs ofthe engine. Lambda map target values are calculated according to thefollowing formula:

    lambda=air-fuel ratio/stoichiometric air-fuel ratio

The lambda target established by the lambda map 77 is combined with airflow data and feedback oxygen levels from the lambda (O₂) sensor 29 tocalculate a gas flow rate 78 for metering valve 9. Data from the gasflow sensor 12 is used to maintain the predetermined gas flow rate tothe metering valve 9. From the metering valve 9, gas is delivered to theintegrated premixture chamber 1 to create the gas/air mixture for enginecombustion.

FIG. 7 illustrates the process control for gas flow sensor 12.Initially, the shutoff valve 13 is maintained in a closed position,blocking fuel flow from fuel source tanks (step 90). The gas tankpressure (P tank) is read, and if the pressure is within a predeterminedhigh-low range, P_(L) -P_(H), the shut-off valve 13 is opened (steps91-92, 94). Of course, if the tank pressure is not within an acceptable,predetermined range, the shutoff valve 13 remains closed (step 93).

After the shut-off valve 13 is opened, the gas flow sensor 12 generatesa gas flow signal Sg, which is a function of the pressure of the gaspassing through the gas flow sensor 12 (steps 94-95). This signal isdependant upon the gas pressure during low or no flow conditions. Atthis point, the gas metering valve 9 reamains closed. If the gaspressure Pg is within an acceptable, predetermined high-low range,P_(SL) -P_(SH), then the gas metering valve 9 is opened, and a fuelcontrol start operation using the gas flow sensor signal for feedbackproceeds (steps 96-98). If the gas pressure Pg is not within the P_(SL)-P_(SH) range, the fuel control start proceeds without the gas flowsensor signal as feedback. Instead, the fuel flow rate employs, forexample, the air flow rate and feedback from the lambda (O₂) sensor 29to control the gas flow (steps 99-100).

FIGS. 8 and 10 illustrate additional embodiments of the presentinvention, which are generally the same as the above describedembodiments and, for that reason, components of these embodiments whichare the same as previously described embodiments have been identified bythe same reference numerals and will not be described again, exceptinsofar as it is necessary to understand the construction and operationof these embodiments.

In FIG. 8, a preferred embodiment of the integrated premixture chamber 1is shown having an air bypass valve 34 to provide for a leaner burnermixture when desired. In conventional internal combustion engines, fueland air are homogeneously mixed before delivery to the engine. A knownmethod to expand the lean burn limit of the fuel/air mixture is toprovide a richer mixture near the spark plug 28 gap itself. The presentinvention provides for the expansion of the lean burn limit of thegas/air mixture by employing the air bypass valve 34 having an intakeport in communication with the lumen 19 upstream from gas/air mixing(designated generally by the numeral 37), and an output port 35 having adistal end located in close proximity to the intake valve.

During a lean burn operation, the air bypass valve 34 is opened and airis delivered to the area about the intake valve, designated generally bythe reference numeral 36. When the intake valve is closed, the airaccumulates near the intake valve. When the intake valve is then opened,air enters first, and then the gas/air mixture, resulting in astratified mix having a richer mixture near the spark plug 28 and aleaner mixture in the lower part of the cylinder. Hence, as is wellknown, the lean burn limit is expanded.

FIG. 9 graphically depicts the results of the stratified charge createdby the embodiment disclosed in FIG. 8. As can be seen, the lean burnlimit due to the instability of engine torque fluctuation is expandedwhen the mixture is less homogenous and more stratified.

Referring now to FIG. 10, another embodiment of the present invention isshown. In this embodiment, an integrated premixture chamber 1 is shownhaving a 3-way gas metering valve 9 for achieving a stratified charge.In this embodiment, the gas metering valve is a 3-way valve 9 having anintake conduit 40, typically made of metal, and in communication withthe gas flow sensor 12 (not shown in this figure). The 3-way meteringvalve 9 also includes a first discharge conduit 39 for discharging gasinto the area upstream of the throttle valve 16 for mixing with air, anda second discharge conduit 38 for discharging gas downstream of thethrottle valve 16 into the area near the intake valve.

In a situation in which the fuel flow into the integrated premixturechamber 1 is low, as when the load on the CNG engine is low, it isdesirable to expand the lean burn limit by the creation of a stratifiedcharge. According to the present invention, gas may be discharged fromthe distal end of discharge conduit 38 after gas is discharged throughconduit 39 where it is mixed with the air. In this manner, because ofthe non-homogeneous nature of the gas and air in the integratedpremixture chamber 1, a stratified charge is achieved in the combustionchamber with a richer mixture following a leaner mixture into thechamber. Alternatively, under normal engine load when the fuel flow rateis high, gas may be supplied simultaneously through both conduits 38 and39, resulting in a more homogeneous mixture (as shown in FIG. 10b).

FIG. 11 illustrates in detail the 3-way metering valve 9 of a preferredembodiment on the invention. As described above, the 3-way meteringvalve 9 includes intake conduit 40, and first and second dischargeconduits 39 and 38. The 3-way metering valve 9 further includes asolenoid coil 41 surrounding an actuator 47, a longitudinal arm 45connecting the actuator 47 to a first valve 42 and a second valve 43.The valves 42 and 43 are biased in a closed position against valve seats48, 49 respectively by a spring 44.

When the coil 41 is energized, the actuator 47 causes arm 45 to move theright as viewed in FIG. 11. This causes valve 42 to open first, openingthe communication between conduit 40 and conduit 39, and allowing thegas to discharge into the upstream portion of the integrated premixturechamber 1. If further energy is supplied to the coil 41, arm 45 isfurther displaced, causing valve 43 to fully separate from contact withthe valve seat 49, thereby permitting fluid flow between conduit 40 andconduit 39. Thus, as can be understood, more gas is delivered to theintegrated premixture chamber 1 to extend the lean burn limit as needed.

From the foregoing descriptions of the various features of the preferredembodiments of the present invention, it can be appreciated that acompact, integrated premixture chamber for accurately controlling themixture of gaseous fuel and air can be provided for more efficient andresponsive engine control and fuel combustion under different operatingconditions, thereby achieving high fuel efficiency and a reduction innoxious exhaust emission.

Although the present invention has been described in detail withparticular reference to preferred embodiments thereof, it should beunderstood that the invention is capable of other and differentembodiments, and its details are capable of modifications in variousobvious respects. As is readily apparent to those skilled in the art,variations and modifications can be affected while remaining within thespirit and scope of the invention. Accordingly, the foregoingdisclosure, description, and figures are for illustrative purposes only,and do not in any way limit the invention, which is defined only by theclaims.

What is claimed:
 1. A premixture apparatus for operating a gaseous fuelinternal combustion engine having a fuel supply means and an air intakemeans, said apparatus comprising:air flow sensing means disposed in saidair intake means for detecting the mass flow rate of air deliveredthrough said air intake means; gas flow sensing means for detecting themass flow rate of gaseous fuel to be supplied to said internalcombustion engine, wherein said gas flow sensing means is located in alongitudinal housing having a lumen defined by said housing, saidhousing further comprising a nozzle on one end thereof constricting saidlumen; gas valve means responsive to said gas flow sensing means andhaving at least one outlet disposed in said air intake means downstreamof said air flow sensing means, for selectively controlling the massflow rate of gaseous fuel supplied to said internal combustion engine;throttle means, having a movable plate disposed in said air intake meansdownstream of the outlet of said gas valve means, for varying thequantity of air and fuel flow through said air intake means; and controlmeans for controlling the operation of said gas valve, said controlmeans being responsive to at least said air flow sensing means and saidgas flow sensing means.
 2. A premixture apparatus according to claim 1further comprising a switching valve means coupled to said gas flowsensing means and having a first open position and a second closedposition, whereby said switching valve means can be switched to the openposition to permit the flow of fuel to said gas flow sensing means orswitched to the closed position to block the flow of fuel to said gasflow sensing means.
 3. A premixture according to claim 1 furthercomprising a throttle position sensing means responsive to varyingpositions in said throttle plate, for actuating said gas valve means toprovide gaseous fuel in response to said throttle plate position;wherein said control means is responsive to at least said air flowsensing means, said gas flow sensing means and said throttle positionsensing means.
 4. A premixture apparatus according to claim 1 whereinsaid air intake means has a longitudinal axis and interior walls withcurved outlets to effect gaseous fuel discharged from the outlet of saidgas valve means to flow in a circuitously swirling fashion within saidair intake means with respect to the longitudinal axis of said airintake means.
 5. A premixture apparatus according to claim 1 whereinsaid air intake means further comprises an area of reduced cross-sectiondisposed in close proximity to the outlet of said gas valve means toeffect an increased velocity and turbulence on gases passing throughsaid area of reduced cross-section.
 6. A premixture apparatus accordingto claim 1 wherein said gas valve means comprises an intake port, afirst valve outlet and a second valve outlet.
 7. A premixture apparatusaccording to claim 1 further comprising an air bypass valve means havingan air intake port and an air outlet, whereby said air intake port is incommunication with said air intake means upstream of the outlet of saidgas valve means, and said air outlet is in communication with said airintake means downstream of said throttle valve means.
 8. A premixtureapparatus comprising a gas bypass valve means according to claim 6,whereby said first gas outlet is in communication with said air intakemeans upstream of said throttle valve means, and said second gas outletis in communication with said air intake means downstream of saidthrottle valve means.
 9. A premixture apparatus according to claim 1further comprising a plurality of outlets downstream of said gas valvemeans for disposing gaseous fuel in said air intake means.
 10. Apremixture apparatus according to claim 9, wherein said gas valve meansis configured such that said second valve outlet is in communicationwith said intake port only after said first valve outlet is incommunication with said first valve outlet.
 11. A premixture apparatusaccording to claim 1 further comprising a main engine control unitcoupled to said control means for communicating sensor related datatherebetween during operation of the internal combustion engine.
 12. Amethod of operating an internal combustion engine having a gaseous fuelsupply source and an air intake passageway coupled to at least onecombustion chamber, said method comprising the steps of:detecting withinthe air intake passageway the mass flow rate of air delivered throughthe air intake passageway; detecting the mass flow rate of gaseous fuelto be supplied to the combustion chamber by measuring the mass flow rateof gaseous fuel passing through a gas flow sensor disposed in alongitudinal housing having a constricted nozzle located on one end ofsaid housing; selectively supplying an amount of gaseous fuel inaccordance with operating characteristics of the engine, to the airintake passageway for intermixing with the air at a location downstreamfrom where the air flow rate is being detected; and regulating athrottle disposed in the air intake passageway downstream of thelocation where the gaseous fuel and air mix, for varying the quantity ofair and fuel flow through the air intake passageway to the combustionchamber in accordance with operating characteristics of the engine. 13.A method according to claim 12 further comprising the step of providinga region of reduced cross-sectional area located where gaseous fuel issupplied within the air intake passageway to effect an increasedvelocity and turbulence on the air and fuel passing within the region ofreduced cross-sectional area in the air intake passageway.
 14. A methodaccording to claim 12 further comprising the step of stratifying themixture of fuel and air by providing an air bypass means having an airintake port and an air outlet, whereby the air intake port is incommunication with the air intake passageway upstream of the locationwhere the gaseous fuel is supplied to the air intake passageway, and theair outlet is in communication with the air intake passageway downstreamof the throttle for supplying air downstream of the throttle.
 15. Amethod according to claim 12 further comprising the step of stratifyingthe mixture of gaseous fuel and air by providing a gas bypass valvehaving a gas intake port and two gas outlets, whereby the first gasoutlet is in communication with the air intake passageway upstream ofthe throttle, and the second gas outlet is in communication with the airintake passageway downstream of the throttle for supplying gasdownstream of the throttle.
 16. An integrated premixture apparatus formixing gaseous fuel and air for delivery to a combustion chamber of aninternal combustion engine coupled to a fuel supply system and to a mainengine control unit, and having an air intake passageway coupled to atleast one combustion chamber, said premixture apparatus comprising:anair flow sensor disposed in said air intake passageway for detecting themass flow rate of air moving through said air intake passageway; a gasflow sensor for detecting the mass flow rate of gaseous fuel supplied tosaid combustion chamber; a gas valve responsive to said gas flow sensorand having at least one outlet disposed in said air intake passagewaydownstream of said air flow sensor, for selectively controlling theamount of gaseous fuel supplied to said combustion chamber; a throttlevalve, having a pivotally secured plate disposed in said air intakepassageway downstream of the outlet of said gas valve, for regulatingthe quantity of air and fuel flow through said air intake passageway; athrottle position sensor responsive to varying positions in saidthrottle plate, for actuating said gas valve to provide gaseous fuel inresponse to said throttle plate position; and a sub-central processorunit located in close proximity to said premixture chamber forcontrolling the operation of said gas valve, said processor beingresponsive to at least said air flow sensor, said gas flow sensor andsaid throttle position sensor, wherein said sub-central processor unitcommunicates engine sensor data to and from said main engine controlunit.
 17. A premixture apparatus according to claim 16 further includinga valve coupled to said gas flow sensor and having a first open positionand a second closed position, whereby said valve can be switched to theopen position to permit the flow of gaseous fuel to said gas flow sensoror switched to the closed position to block the flow of gaseous fuel tosaid gas flow sensor.
 18. A premixture apparatus according to claim 16wherein said air intake passageway has a longitudinal axis and interiorwalls with curved outlets to effect gaseous fuel discharged from theoutlet of said gas valve to flow in a circuitously swirling fashionwithin said air intake passageway with respect to the longitudinal axisof said air intake passageway.
 19. A premixture apparatus according toclaim 16 wherein said air intake passageway further comprises an area ofreduced cross-section disposed in close proximity to the outlet of saidgas valve to effect an increased velocity and turbulence on gasespassing through said area of reduced cross-section.
 20. A premixtureapparatus according to claim 16 wherein said gas valve comprises anintake port, a first valve outlet and a second valve outlet, wherebysaid gas valve means is configured such that said second valve outletcommunicates with said intake port only after said first valve outlet isin communication with said intake port.
 21. A premixture apparatusaccording to claim 16 further comprising an air bypass valve having anair intake port and an air outlet, whereby said air intake port is incommunication with said air intake passageway upstream of the outlet ofsaid gas valve, and said air outlet is in communication with said airintake passageway downstream of said throttle valve.
 22. A premixtureapparatus according to claim 16 further comprising a gas bypass valvehaving an gas intake port and two gas outlets, whereby said first gasvalve outlet is in communication with said air intake passagewayupstream of said throttle valve, and said second gas outlet is incommunication with said air intake passageway downstream of saidthrottle valve.